Formation of dyes suited for reproduction purposes

ABSTRACT

DIAZO RECORDING PROCESS GIVING A NEUTRAL BLACK TONE USING AS THE COUPLING AGENT IN AN ALKALINE MEDIUM A QUATERNARY SALT OF 2-METHYL-5,6-DIMETHOXYBENZOTHIAZOLE OR A QUATERNARY SALT OF 2-METHYLBENZOTHIAZOLE WHEREIN THE CARBON ATOMS OF THE 5- AND 6-POSITION ARE PART OF A FUSED RING CLOSED BY A -O-CH2-O- OR A   -O-CH2-CH2-0-   GROUP. PREFERABLY THE QUATERNARY SALT IS SUBSTITUTED ON THE NITROGEN ATOM OF THE BENZTHIAZOLIUM NUCLEUS WITH A   -CH2-Y   GROUP IN WHICH Y IS AN ELECTRON-WITHDRAWING GROUP SUCH AS IN A -CH2-CO-NH-SO2-CH3 GROUP; AND RECORDING MATERIALS USEFUL THEREIN.

United States Patent 01 ice- 3,676,138 Patented July 11, 1972 3,676,138 FORMATION OF DYES SUITED FOR REPRODUCTION PURPOSES Albert Lucien Poot, Kontich, and Henri Depoorter, Mortsel, Belgium, assiguors t Agfa-Gevaert, Mortsel, Belgium No Drawing. Filed Dec. 2, 1970, Ser. No. 94,574 Claims priority, application Great Britain, Dec. 3, 1969, 59,093/ 69 Int. Cl. G03c 1/58, /22, 5/34 U.S. CI. 96-75 16 Claims ABSTRACT OF THE DISCLOSURE Diazo recording process giving a neutral black tone us ing as the coupling agent in an alkaline medium a quaternary salt of 2-methyl-5,6-dimethoxybenzothiazole or a quaternary salt of Z-methylbenzothiazole wherein the carbon atoms of the 5- and 6-position are part of a fused ring closed by a OCH -O or a -O--CH CH O group. Preferably the quaternary salt is substituted on the nitrogen atom of the benzthiazolium nucleus with a CH Y group in which Y is an electron-withdrawing group such as in a --CH CONHSO CH group; and recording materials useful therein.

This invention relates to the formation of dyes, to recording and reproduction of information and to the use of particular chemical compounds in the diazo recording process.

As is known the diazo recording process is based on the fact that certain diazo compounds, e.g. diazonium salts, can be decomposed information-wise by light under nitrogen evolution. The remaining diazo compound can react with a so-called coupler to form a dye.

In the dry diazo process, also called two-component diazo system, the recording material contains a diazonium compound and a coupler in intimate contact therewith in the same layer. In addition, it contains an acid that prevents the premature reaction of the diazonium compound and the coupler. After the recording material has been exposed to ultraviolet light passing through the original, it is treated with a volatile base such as ammonia. This neutralizes the acid and allows the remaining diazonium compound to combine with the coupler and to form a dye in the image areas.

In the wet or moist diazo process, also called one-component diazo system, the recording material contains only the diazonium compound. After the recording material has been exposed imagewise to ultra-violet light, it is treated with an alkaline solution containing the coupler. The remaining diazonium compound couples with the coupler in the non-exposed areas.

Usual couplers are aromatic hydroxy compounds such as phenols and naphthols of which 2,3-dihydroxynaphthaleen-6-sulphonic acid is a typical example.

Other known couplers contain a reactive methyl or methylene group as described in Belgian patent specification 459,543 filed Aug. 3, 1945 by Gevaert Photo-Producten NV. and US. patent specification 2,532,744 of James M. Straley, issued Dec. 5, 1950. Typical examples of the latter class are quaternary salts of Z-methylquinoline, Z-methylthiazoline and 2-methylbenzothiazole, and N-methyl-Z-methylene-benzothiazoline.

In diazotype printing it is very diflicult to obtain a black print with one diazonium compound and one coupler.

Therefore practically always mixtures of couplers and/or diazonium compounds had to be used that yield a mixture of dyes approximating the ideal neutral black.

Owing to the difference in light-sensitivity, storage stability and coupling reactivity of the different imaging compounds and to the difference in stability to light of the respective dyes formed on coupling, it is very difficult to obtain neutral black prints that do not change in colour tone by time.

It is one of the objects of the present invention to provide a diazo recording process and materials by means of which images having a neutral black tone can be obtained.

It has now been found that dyes with a neutral black colour tone can be produced by the coupling of a diazonium compound with a quaternary salt of 2-methyl-5,6- dimethoxybenzothiazole and/or a quaternary salt of 2- methylbenzothiazole the carbon atoms of which in the 5- and 6-position make part of a fused ring closed by a -0CH -O- or -OCH -CH -O- group.

Quarternary salts that are preferably used in the recording process and materials according to the present invention correspond to one of the following general Formulae I and II:

R represents a substituent introduced by quaternization, e.g. an aliphatic group, including a cycloaliphatic group, a saturated aliphatic group, an unsaturated aliphatic group, or one of said groups in substituted form, e.g. an alkyl group, more particularly a C C alkyl group, an allyl group, a cycloalkyl group, e.g. a cyclopentyl or cyclohexyl group, a substituted cycloalkyl group, a substituted alkyl group, e.g. an aromatically substituted alkyl group, e.g. a benzyl group, a phenyl ethyl group, a substituted aralkyl group, e.g. a carboxybenzyl group, a sulphobenzyl group, a halogenated benzyl group, e.g. a bromo-benzyl group, a hydroxy-benzyl group, a hydroxyalkyl group, a carboxyalkyl group, a sulphoalkyl group, a

sulphatoalkyl group, a phosphoalkyl group, a phosphoester-substituted alkyl group, an acetoXy-alkyl group, wherein the alkyl group preferably contains from 1 to 4 carbon atoms, such as in fi-hydroXyethyl, B-acetoxyethyl, sulphopropyl, sulphobutyl, phosphopropyl, propyl sulphate, and butyl sulphate, further the substituted alkyl group A-(|J|'-O-BSOz-OM wherein M is hydrogen, an onium group or a metal atom, B represents a lower alkylene group such as methylene, ethylene, propylene or butylene group, and A represents a methylene group or (examples of such substituted alkyl group are described in the United Kingdom patent specification 886,271 filed June 20, 1957 by Gevaert Photo-Producten N.V., e.g. a sulphocarbomethoxymethyl group, an w-sulphocarbopropoxymethyl group, a p-(w-sulphocarbobutoxy)-benzyl group), and further the substituted alkyl group --A W-NI-I-V-B wherein A represents a lower alkylene group such as methylene, ethylene, propylene,

or butylene group; B represents an alkyl group, an

amino group, a substituted amino group and also a hydrogen atom if V is a single bond, and W and V each represents a -CO-radical, a --SO -radical or a single bond but at least one of them being a SO -radical (examples of such substituted alkyl groups are described in the United Kingdom patent Specification 904,332 filed July 5, 1957 by Gevaert Photo-Producten N.V., e.g. a

N-(methyl-sulphonyl)-carbamyl-methy1 group, a 'y- (acetylsulphamyl)-propyl, or a 6-(acetyl-sulphamyl)- butyl group),

n represents 1 or 2, and

X- represents an anion, e.g. a chloride, bromide, iodide, perchlorate, thiocyanate, benzene sulphonate, p-toluene sulphonate, methyl sulphate, ethyl sulphate or a propyl sulphate anion, but X is missing if the anion is already contained in the R group (betaine salt form).

The quaternary 2-methyl-5,6-dimethoxy-benzothiazolium compounds can be prepared by quarternization of the corresponding bases. For illustrating the preparation of a preferably used benzothiazolium compound the following receipt is given:

Preparation of 2-methyl-3-N-(methylsulphonyl)-carbamylmethyl-5,6-dimethoxy benzothiazolium bromide A mixture of 52 g. of Z-methyl-5,6-dimethoxybenzothiazole and 55 g. of N-(bromoacetyl)-methanesulphonamide were heated on an oil bath at 110-115 C. for 1 h. Thereupon the reaction mass was cooled, pulverized, and washed with acetone and diethyl ether, yielding about 100 g. of quaternary salt.

The starting Z-methyl-5,6-dimethoxybenzothiazole was prepared according to K. Fries, H. Koch and H. Stukenbrock, Liebigs Ann. Chem., 468, 170 (1929) or J. D. Kendall and H. Suggate, J. Chem. Soc, 1503 (1949).

The benzothiazole compound having the following structural formula:

5d its quaternary salts can be prepared according to A. I. Kiprianov and G. M. Golubushina Ukrain. Khim. Zh. 29, 1172 (1963).

The benzothiazole compound having the following structural formula \CCH3 CH2 I and its quaternary salts can be prepared according to J. D. Kendall and H. G. Suggate, J. Chem. Soc. 1503 (1949).

For obtaining a neutral black dye by coupling With the couplers used according to the present invention preferably diazonium compounds are used, 'Which are prepared by diazotation of primary aromatic amines containing in para-position with respect tothe primary amino group a tertiary amino group such as a dialkylamino group.

Typical examples of such amines are p-aniino-N,N-diethylaniline and p-amino-N-ethyl-N-benzylaniline.

Particularly useful in this invention are the diazonium compounds corresponding to the following structural formulae:

[ GQ L Q] znoli (diazo 14 It is assumed that the quaternization, more particularly the type of the R radical, has an influence on the speed of production of the black dye. Indeed, it has been discovered that if the R group is a CH -Y group, wherein Y is a negative or electron-Withdrawing radical, a black dye is formed very rapidly. So, preferably the Y group contains a carbonyl group, which is directly linked to the CH radical.

Taking into account the preceding a preferably used coupler has the following structural formula:

(1) W CHa HaCO Other suitable couplers, which, however, do not immediately yield a black dye on coupling with a diazonium salt by treatment with gaseous ammonia vapour correspond to the following structural formulae:

The initial colour obtained with said couplers on coupling with diazo 69 is violet to dark violet and turns into neutral black on storage.

The quaternary salts of 2 methyl 5,6-dimethoxybenzothiazole can be used successfully in the one-component as well as in the two-component diazo system.

Said quaternary salts can further be used in a so-called thermodiazo process. In such a process a recording material containing such a quaternary salt as coupler, a diazonium compound, a pH-reducing compound to prevent premature coupling, and optionally a compound forming or releasing a base on heating (e.g. urea) is (l) exposed information-wise to electromagnetic radiation that decomposes information-wise the diazonium compound and (2) is overall heated, whereby coupling takes place in accordance with the non-exposed portions of the recording material.

Diazo recording materials according to the present invention contain the diazonium compound preferably in a flexible sheet or supported flexible layer.

Suitable supports or layers used in copying materials according to the present invention have liquid-absorbing characteristics as e.g. ordinary wood pulp paper or rag type paper but also textiles including fabrics made of cotton, cellulose acetate, regenerated cellulose, in other words all types of woven or felted materials, which can be impregnated with a solution containing one or more of the diazonium compounds and/ or couplers.

For producing transparent diazo prints a transparent sheet is used as support, e.g. a water-impermeable resin sheet. In that connection reference is made to the usual transparent film supports of silver halide photography. When a water-impermeable resin sheet is used as a sup port, the imaging chemicals are preferably incorporated into a hydrophilic colloid layer, e.g. a gelatin-containing layer.

The radiation-sensitive coating composition containing a diazonium compound may contain all kinds of other ingredients, e.g. wetting agents, substances generating a base on heating, or a thermally activatable base-releasing material, e.g. urea and the substances used for that purpose described, e.g., in the United Kingdom patent specification 983,363, filed May 8, 1961, by Nashua Corporation and the French patent specifications 1,376,708 and 1,37 6,- 709 both filed Sept. 17, 1963, by Et. Bauchet Co., further optical brightening agents, pigments, e.g. silica, and antioxidants improving the whiteness of the areas in which the diazonium compound has been destroyed. Suitable antioxidants are thiourea, ascorbic acid and allyl isothiocyanate in concentrations ranging from to 25 percent by weight in respect of the diazonium salts.

Preferred amounts of diazonium compound and coupler per sq. m. are in the ranges of 0.1 g. to 0.5 g. and 0.1 g. to 1.5 g. respectively.

A good storage stability of a coating composition containing a diazonium compound and a coupler according to general Formula I can be obtained by using an admixture with said compounds an acid, e.g. citric acid, tartaric acid, boric acid, trichloroacetic acid, tribromoacetic acid, sulphosalicylic acid, phosphoric acid or 1,3,6-naphthalene trisulphonic acid disodium salt in an amount of 100 to 200 percent by weight in respect of the diazonium salt.

Obviously all known principles for preventing premature coupling can be applied in order to obtain a recording material with a storage stability as high as possible. In that connection is mentioned, e.g., keeping apart the diazonium compound and the coupler by means of a meltable layer or capsule envelope.

Whenever in the present invention the term diazo compounds is used this term includes the diazonium salts prepared by diazotation of an aromatic amine but also the diazonium salts produced from diazo sulphonates, which compounds may also be employed in a diazo recording process according to the present invention.

The following examples illustrate the present invention. The percentages are by weight if not otherwise indicated.

EXAMPLE 1 A coating composition was prepared by mixing the following ingredients until dissolution of the water-soluble compounds thereof: p-Diethylaminobenzene diazonium tetrafluoroborate (diazo 69) g 6 2-methyl 3 methylsulphonylcarbamylmethyl 5,6-

dimethoxy benzothiazolium bromide (coupler l) g 8 Citric acid g 40 Naphthalene-trisulphonic acid trisodium salt g 8 25% aqueous solution of naphthalene-trisulphonic acid disodium salt ml 56 Urea g Colloidal silica g 1 Saponine g 0.5 Water, up to 400 ml.

The composition was coated onto a paper base in a proportion of 19 g. per sq. m. and after drying exposed 6 through a line diapositive with ultraviolet light in a common diazotype copying apparatus.

Development proceeded by a treatment with gaseous ammonia.

Immediately a positive neutral black print was formed on a colourless background.

EXAMPLE 2 Example 1 was repeated but instead of the benzothiazolium coupler a same amount of coupler according to the general Formula I was used, wherein R=C H and X: (C l-1 (coupler 2).

The colour formed initially was violet and turned rapidly into neutral black.

EXAMPLE 3 Example 1 was repeated but instead of the benzothiazolium compound a same amount of coupler according to the general Formula I was used, wherein and X-=Br- (coupler 3).

The colour formed initially was violet and after a few .minutes turned into neutral black.

EXAMPLE 4 Example 1 was repeated but instead of the benzothiazolium compound a same amount of coupler according to the general Formula I was used, where p-Diethylaminobenzene diazonium tetrafluoroborate (diazo 69) g 1.5 g 2 Citric acid g 10 Naphthalene-trisulphonicacid trisodium salt g 2 25% aqueous solution of naphthalene-trisulphonic acid disodium salt ml 14 Urea g 5 Saponine g 0.1 Ethylene glycol ml 5 Water, up to ml.

1 Formula mo o-on.

| ILL HaSOF HzC The composition was coated onto a paper base in a proportion of 19 g. per sq. m. and after drying exposed through a line diapositive with ultra-violet light in a common diazotype copying apparatus.

Development proceeded by a treatment with gaseous ammonia.

The colour formed initially was dark violet and turned into neutral black on storage.

We claim:

1. A diazo recording process, which comprises the coupling in alkaline medium of a diazonium compound with s o moo \H CH3 4 fiT X- o 11300 N L X wherein R represents an aliphatic group including a cycloaliphatic group, a saturated aliphatic group, an unsaturated aliphatic group or one of said groups in substituted form n represents 1 or 2, and

X represents an anion, but X- is missing when the anion is already contained in the R group.

3. A process according to claim 2, wherein the quater' nary salt contains an R group that stands for -CH Y, wherein Y is an electron-withdrawing group.

4. A process according to claim 3, wherein a quaternary salt is used, which corresponds to one of the following structural formulae:

5. A process according to claim 1, wherein the quaternary salt coupler is used in a so-called two-component or one-component diazo recording system.

6. A process according to claim 1, wherein a recording material containing an intimate mixture of the quaternary salt, the diazonium compound and a pH-reducing compound to prevent premature coupling, is exposed information-wise to electromagnetic radiation that decomposes the diazonium compound in the irradiated portions, and the recording material is non-differentially heated in order to produce a dye with the diazonium compound remaining in the non-exposed portions of the recording material.

7. A process according to claim 1, wherein the diazonium compound is a diazonium salt prepared by diazotation of a primary aromatic amine that contains a tertiary amino group in para-position with respect to the primary amino group.

8. A process according to claim 7, wherein the diazonium salt corresponds to one of the following structural formulae:

9. A photosensitive recording material comprising a self-supporting sheet or supported layer containing a diazonium compound and a quaternary salt of 2-methyl-5,6- dimethoxybenzothiazole and/or a quaternary salt of 2- methylbenzothiazole wherein the carbon atoms of the 5- and 6-position make part of a fused ring closed by a 01' group.

10. A photosensitive recording material according to claim 9, wherein the quaternary salt corresponds to one of the following general formula:

O s H3 00 TUBE CH3 H 00 is X or L X- 111 o y wherein R represents an aliphatic group including a cycloaliphatic group, a saturated aliphatic group, an unsaturated aliphatic group, or one of said groups in substituted form,

n is 1 or 2, and

X'- represents an anion, but X- is missing when the anion is already contained in the R-group.

11. A recording material according to claim 10, wherein R in the general formula stands for the group -CH Y, wherein Y represents an electron-withdrawing group.

12. A recording material according to claim 9, which contains in admixture with the quaternary salt and the diazonium compound a pH-reducing compound to prevent premature coupling.

13. A recording material according to claim 9, which contains in admixture with the quaternary salt and the diazonium compound a compound forming or releasing a base on heating.

14. A recording material according to claim 9, wherein the recording material contains a paper support.

15. A recording material according to claim 9, wherein the recording material contains a transparent resin support.

16. A dye produced by the coupling of a diazonium compound and a quaternary salt of 2 methyl 5,6- dimethoxybenzothiazole and/or a quaternary salt of 2- methylbenzothiazole wherein the carbon atoms of the 5- and 6-position make part of a fused ring closed by a OOCH O or -OCH CH -O group.

References Cited UNITED STATES PATENTS 3,615,570 10/1971 Werner et a1 96-49 X 3,563,752 2/1971 Werner et a1. 96-49 X 3,389,996 6/1968 Welch 96--49 3,164,469 1/1965 Behmenburg et al. 96-49 3,415,807 12/1968 Fisher 260158 3,346,585 10/1967 Denert 260158 3,525,733 8/1970 Weaver 260158 3,245,981 4/1966 Stright 260158 NORMAN G. TORCHIN, Primary Examiner J. L. GOODROW, Assistant Examiner U.S. Cl. X.R. 96--9l, 49

UNITED STATES PATENT OFFICE CERTIFICATE OF CURRECTION Patent No. 3 r 676 r 138 Dated July ll, 1972 lnventofls) Albert Lucien POOT et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, Claim 4, lines 50-55, fourth formula, correct to read as follows:

T n H C Column 8, Claim 16, line 57, correct the line to read as follows: -OCH O or OCH CH O group.

Signed and sealed this 17th day of October 1972.

(SEAL) Attest:

EDWARD M .FLETCHER,JR ROBERT GOT TSCHALK Attesting Officer Commissioner of Patents FORM PC4050 USCOMM-DC 60376-P69 U.S GOVERNMENT PRINTING OFFICE: 959 0-355-334 

